The palladium catalyzed arylation of olefins (the Heck reaction) is one of the most versatile tools for C—C bond formation in organic synthesis.[1] Phosphine ligands are generally used to stabilize the reactive palladium intermediates, and excellent results have been reported for Pd-catalyzed Heck reactions when sterically bulky mono-phosphines, diphosphines, cyclometalated phosphines, or phosphites are used as the ligands.[2-5] The air-sensitivity of phosphine ligands, however, places significant limits on their synthetic applications. Therefore, the development of phosphine-free palladium catalysts is a topic of enormous interest.[6-8] Thioureas are air and moisture stable solids and have recently been, employed as ligands in Ru—, Rh—, or Pd-catalyzed reactions.[9-10] Very recently, Z. Yang[11] and coworkers reported the Heck and Suzuki reactions of highly active arenediazonium salts catalyzed by a chiral thiourea -Pd complex.